Cemal Saydam

The role of atmospheric deposition in the biogeochemistry of the Mediterranean Sea

Abstract Estimates of atmospheric inputs to the Mediterranean and some coastal areas are reviewed, and uncertainities in these estimates considered. Both the magnitude and the mineralogical composition of atmospheric dust inputs indicate that eolian deposition is an important (50%) or even dominant (>80%) contribution to sediments in the offshore waters of the entire Mediterranean basin. Model data for trace metals and nutrients indicate that the atmosphere delivers more than half the lead and nitrogen, one-third of total phosphorus, and 10% of the zinc entering the entire basin. Measured data in sub-basins, such as the north-western Mediterranean and northern Adriatic indicate an even greater proportions of atmospheric versus riverine inputs. When dissolved fluxes are compared (the form most likely to impinge on surface water biogeochemical cycles), the atmosphere is found to be 5 to 50 times more important than rivers for dissolved zinc and 15 to 30 times more important for lead fluxes. Neglecting co-limitation by other nutrients, new production supported by atmospheric nitrogen deposition ranges from 2–4 g C m−2 yr−1, whereas atmospheric phosphorus deposition appears to support less than 1 g C m−2 yr−1. In spite of the apparently small contribution of atmospheric deposition to overall production in the basin it has been suggested that certain episodic phytoplankton blooms are triggered by atmospheric deposition of N, P or Fe. Future studies are needed to clarify the extent and causal links between these episodic blooms and atmospheric/oceanographic forcing functions. A scientific program aimed at elucidating the possible biogeochemical effects of Saharan outbreaks in the Mediterranean through direct sampling of the ocean and atmosphere before and after such events is therefore highly recommended.

Heavy metal concentrations in surface sediments from the two coastal inlets (Golden Horn Estuary and İzmit Bay) of the northeastern Sea of Marmara

A total of 57 surficial sediment samples collected in the Golden Horn Estuary and Izmit Bay (northeastern Marmara Sea) was analyzed for the heavy metals Fe, Mn, Cr, Ni, Co, Zn, Pb, and Cu and the results were compared with various natural and anthropogenic sources. It was observed that the concentrations of Zn, Cu, Pb, and, to some extent Cr, in the Golden Horn sediments are comparable with those in most other seas in the vicinity of highly industrialized and densely populated regions. Based on calculations from the metal: Al and metal: Fe ratios, the bottom sediments of Golden Horn were found to be enriched in Zn, Cu, Pb, and to a lesser extent Cr, by factors of up to 192 compared with the regional background levels of these metals. Fe, Mn, Co, and to some extent Ni, are mostly at natural levels. In contrast, the metal levels of the bottom sediments in Izmit Bay are significantly lower and they appear to be controlled by lithogenic rather than the anthropogenic influences. Highly significant correlation coefficients between the metals Zn, Cu, and Pb are widely attributed to the common sources of these metals, the metal smelters and shipyards in the vicinity of the areas studied. Based on the numerical value of the geoaccumulation index of heavy metals, it was found that the bottom sediments of Izmit Bay can be regarded as basically uncontaminated. Exceptionally high Igeo values are found for the bottom sediments of the Golden Horn, indicating moderate to extreme contamination in this region by the metals Pb, Zn, Cu, and Cr. The presence of a large number of anthropogenic metal point sources, higher river run-off via the two major creeks, particularly coastal topography and hydrodynamic conditions, associated with the very high sedimentation rates, all strongly favour the accumulation of anomalously high metal concentrations in the Golden Horn Estuary, while the opposite is true for Izmit Bay.

Transport and distribution of nutrients and chlorophyll-a by mesoscale eddies in the northeastern Mediterranean

Abstract The distribution of nutrient elements and chlorophyll- a in the Northern Levantine Basin (NLB) were investigated in some detail and are discussed together with the physical aspects of the region in the present study. The surface circulation pattern of the NLB was studied and the structure of the relatively large-scale Rhodes cyclonic gyre, which is located between Rhodes and Cyprus, was investigated for the same time period. The most important characteristics of this cyclonic gyre are the upwelling of nutrient-rich deep waters within the gyre and the reverse phenomenon at the peripheries. Anticyclonic circulation systems generally surround the Rhodes cyclonic gyre; the permanent ones are located in the southern part of the Rhodes gyre, in the Cilician Basin, and off Iskenderun Bay. The vertical distribution of nutrients in the water column shows completely reversed trends and the nutrient gradient ranges between 300–400 m in the central parts of the anticyclonic systems. Thus downwelling processes also occur in the NLB and the formation of Levantine Intermediate Water (LIW) observed in the NLB matches the chemical data presented here. This special vertical and spatial distribution of nutrients affects the distribution of the phytoplankton population, as the patches of primary producers are aggregated in the central parts of the Rhodes gyre. This is confirmed by the chlorophyll- a data and the unexpected content of neuston net collection in the same region. The concentration of chlorophyll- a was relatively high at offshore stations, such as in the central parts of the cyclonic gyres, where zooplankton, small shrimp and fish larvae, etc., were observed in large quantities.

Identification of the oxic/anoxic interface by isopycnal surfaces in the black sea

The analysis of hydrochemical data collected in the Black Sea since 1987 shows that the upper boundary of the oxic/anoxic interface zone coincides with the nitrate maximum at the depths of σ t ⋍ 15.40 ± 0.10 isopycnal surface. Its lower boundary corresponds to the phosphate maximum depth at σt ⋍ 16.20 ± 0.05 isopycnal surface, independent of the geographical location and seasion. In the absence of the continuous pump cast measurement system, and when the oxygen and sulphide concentrations are too low to be measured with sufficient precision within the interface zone, such features of the oxygen-nitrate and H2S-phosphate correlations at specific density levels provide a direct and practical way to identify the oxic/anoxic interface zone. This, in turn, allows for a more precise and systematic water sampling for studying the complex biogeochemistry of the layer.

Vertical variations in the principle chemical properties of the Black Sea in the autumn of 1991

Abstract Basin-wide principal hydrochemical data for the upper 500 m of the Black Sea were obtained at a total of 197 stations during a multi-ship, multi-institutional, Hydroblack -91 cruise in September 1991. Only offshore stations, 38 from the 1991 joint cruise, 5 from R/V Knorr (1988), 16 from R/V Atlantis-II (1969), and 9 from R/V Bilim (1990) cruises, are considered in conjunction with the present and past data as a function of potential density rather than depth. The oxycline, coinciding with the upper boundary of the permanent pycnocline (σΘ = 14.2–14.3), extended down to the σΘ = 15.3–15.4 surfaces during warm periods (June–September) and to the σΘ = 15.75 surface during spring periods. The lower boundary of the oxycline (O2 ⩽ 20 μM) has remained constant within the last two decades when past and present spring data are considered, but has risen by 0.30 density units when late summer-autumn data are considered. Independent of the geographical location, the base of the transition layer was established at the σΘ = 16.15–16.20 surfaces where H2S ⩾ 5 μM. Nitrate and phosphate reached their maxima at σΘ = 15.3–15.4 surfaces and then decreased steadily with different slopes until the σΘ = 15.85 –15.95 surfaces. At the anoxic interface, phosphate concentration increases about 10 fold from ∼ 0.02 –0.5 μM at the σΘ = 15.85 –15.90 surface to 4 –6 μM at the σΘ = 16.15 –16.20 surface. Comparison with the data from the 1970s suggests that both the maximum values and the depth integrated mass of nitrate (g NO3—N/m2) between the σΘ = 14.2 and 16.0 surfaces have increased 2–3 fold, and the density surface where the NO3 maximum is established has shifted by 0.30 units in the late 1980s.

African dust-laden atmospheric conditions activate the trigeminovascular system

It has been recently noticed that dust originating from deserts can be transported to other continents by the atmosphere and has an adverse effect on public health, such as increased asthma attacks. Dust originating from the Saharan Desert could initiate a series of reactions upon contact with cloud water and results in the formation of reduced iron (Fe2+), oxalate and various basic amino acids. We aimed to evaluate whether the simulation of Saharan dust-containing atmospheric conditions could trigger the trigeminovascular system. Freely moving rats incubated within simulated atmospheric conditions containing (i) Saharan dust, (ii) Co60 gamma ray-treated Saharan dust (sterilized) and (iii) dust-free air, were investigated for the presence of c-fos expression in trigeminal nucleus caudalis (TNC) and for NOx (nitrate+nitrite) levels in blood samples. Atmospheric samples were analysed for microorganisms. Saharan dust-containing atmospheric conditions induced c-fos expression in nociceptive neurons within TNC. The number of c-fos+ neurons in superficial lamina of TNC was significantly higher in the Saharan dust group (32.9 ± 5.3, P = 0.0001) compared with dust-free air (11.02 ± 2.7) or Co60-treated Saharan dust groups (15.01 ± 2.4). An increase in NOx levels was detected in blood samples of rats exposed to Saharan dust-containing atmosphere. This study has revealed an unknown environmental factor as a possible trigger for headache. It is the first time that transport of Saharan dust with the atmospheric air stream has been documented to be able to trigger the trigeminovascular system in animals. Further studies are needed to explore the mechanisms and molecules that mediate the nociceptive effect and to guide new treatment strategies.

Distribution of tin in the northeastern Mediterranean

Abstract Concentrations of tin, one of the naturally methylated elements, was determined in sea water, sediments and organisms, collected from the Northeastern Mediterranean. A hydride generation technique was employed, in which the tin and methyltin, were converted to their hydrides. The hydrides produced were detected by atomic absorption spectrophotometer. On the average, the inorganic tin content of sea water samples ranged between 1.1–236 ng/1. Although the dominant methyltin species was dimethyltin, all forms of methyltins (mono, di and tri-methyltins) were detected. The sediment samples were analyzed for the acid extractable tin content and the concentrations were found to range between 0.17–2.30 ug/g (dry weight). Methyltin concentration ranged between 0.1–9.7 ng/g (dry weight). The organism (Limpet) samples were analyzed for their total tin and methyltin contents. Total tin ranged between 7.2–564 ng/g (dry weight), and the methyltins ranged between 0.5–13.9 ng/g (dry weight).

The Determination of Trace Metals in Marine Organisms by Atomic Absorption Spectrometry

Abstract The application of atomic absorption spectrometry to the analysis of trace metals in marine organisms is described. The samples are digested with nitric acid in teflon decomposition vessels. Mercury is determined by the cold-vapor method while the other elements are determined by flame atomization or flameless graphite-furnace atomization. Several marine species of economic importance. are analyzed for seven trace elements.

Long term impact of dissolved dispersed petroleum hydrocarbons (DDPH) in Gulf of Iskenderun

Abstract DDPH in sea water, polyaromatic hydrocarbons (PAHs) in sediment and in some marine biota were monitored for the period of August 1981 and April 1984. Maximum DDPH was measured in winter and minimum in summer. This phenomena showed an inverse relation with the sea water temperature. Increase in sea water DDPH concentration reflected itself immediately in fish liver but two months time lack between fish liver and flesh was observed. GLC analysis results of sea water extracts and various crude oil showed that the petroleum hydrocarbons in the Gulf was mainly originated from Kirkuk crude oil.

Aerosol Nitrate and Non-Sea-Salt Sulfate Over the Eastern Mediterranean

Among the biogenic sources of sulfate aerosols, reduced sulfur gases such as DMS constitute and control a significant fraction of the atmospheric nss-sulfate budget (Charlson et al., 1987, e.g.). Certain species of phytoplankton; particularly the dinoflagellate Phaeocystis pouchetii and the coccolithophore Emiliana huxleyi are known to be important producers of dimethylsulfide (DMS) (Matrai and Keller, 1993, e.g.). Biogenic sulfur, created mainly by seasonal phytoplanktonic activity, could be particularly rich sources in certain regions and dominate the atmospheric sulfur cycle.